3D Vision Blog

A normal user's look into the world of 3D Stereo Technologies

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Quick Test for Vision Acuity for Better Stereoscopic 3D Viewing

January 21st, 2013 · 1 Comment · Other S3D Tech

I’ve already talked multiple times about how vision issues can lead to bad experience when viewing stereoscopic 3D content, but still a lot of people believe that their vision is good enough and it is certainly not causing them any problems, and instead the stereo 3D content is bad or the technology is not good enough. And while the case may be that you are watching some bad quality 2D to 3D conversion, or using bad quality S3D viewing technology, even the viewing conditions may not be good enough and so on resulting in a bad experience, you could also have some issues with your vision as well. Have in mind that having trouble when watching stereo 3D content can be a hint that you need to go to a specialist to examine your eyes as you might just need to get a glasses (or new ones if you are already wearing prescription glasses), but sometimes there could be a more serious issue that needs extra attention. Having a normal vision (normal visual acuity), often referred to as 20/20 vision or 6/6 vision is good sign that your eyes are Ok and if you are experiencing trouble when watching stereoscopic 3D content, then the issue might be in something else. You need to be sure that the problem is not within your eyes as good eye health and proper vision is important in our everyday life and not only for watching stereo 3D content. Having vision problems such as nearsightedness (myopia), farsightedness (hyperopia), astigmatism or presbyopia can also cause issues with having good experience when watching stereoscopic 3D content, so if you suffer from any of those you will need to wear the proper prescription glasses or lenses in order to correct them and have normal vision restored.

How do you know if you need to go see a specialist and have your eyes examined? I’ve already mentioned that having trouble when watching stereoscopic 3D content such as experiencing headache, dizziness, disorientation or nausea while watching or after watching something in stereo 3D is a good sign that you might need to go see a specialist. But you can use another simple test that can help you give you an idea on what is your vision acuity at home and see if you need to go to a specialist and have your vision examined. All you need is a printer and a friend to help you take a test of your vision by using a version of the popular Snellen eye chart, variation of which is often used by eye care professionals to check patient’s vision. You need to download and print the eye chart from the link below (A4 size version and Letter version available), make sure you use the actual size when printing and don’t resize to fit. Then hang it on a wall in a well lit room (including the chart) with a friend staying next to the chart to help you take the test, measure 10 feet (or 3 meters) from the chart and stand there. Normally the distance is 20 feet or 6 meters with larger chart, but since you may have trouble finding the needed space the charts have been resized for taking the test at half that distance. To take the test you need to first cover one of your eyes with the palm of your hand and try to read aloud all the letters you see line by line the best you can, and the person helping you checks if you have read them correctly marking where and how many mistakes you make (if you make any). Then you change the eyes and repeat the procedure again with the person helping you noting where you make mistakes, if you make any, so that you can compare the results from both eyes as they may have different level of vision acuity.

And now comes the time to check the results. If you are able to read without making any mistakes all of the letters top to the bottom of the chart with both eyes, this means that you have what is considered to be normal vision (maybe even better than that), so you have no reason to worry. If you are having trouble reading without a mistake not only the bottom line, but the 2-3 of the ones above it, then you probably have a near-normal vision which normally should not cause you problems, but it is still a good to check your eyes. The suggestion to go see a specialist is even more important if you have a difference of two or three lines from the chart that you have no trouble reading with one of your eyes and the other. If you are having trouble properly reading even higher lines in the chart or the difference between what you can read with your left eye is even bigger than with your right eye you must go and see a specialist to have your vision examined. If you are already wearing contact lenses or prescription glasses you might want to do the test with and without wearing them to see what will be the results. This way the test may also give you an idea if you need to increase or decrease the diopter you currently have in case your vision has improved or became worse than the last time you’ve had it examined.

Have in mind that this simple way to check your vision is just to give you a basic idea on how good it is and is intended more to give you a hint if you need to go and see a specialist and have your eyes examined. It is not intended to replace a proper eye examination by a specialist, it might just point out the need for doing such an exam! Have in mind that the above test is not intended to directly check for potential problems of your stereoscopic vision, it is for checking the vision acuity. I do hope that you find this useful…

To download the test Snellen eye chart for printing on A4 size paper…
To download the test Snellen eye chart for printing on Letter size paper…

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More About the Possible Health Risks Associated With Stereo 3D

August 12th, 2010 · 10 Comments · Other S3D Tech

At the moment a lot of people are concerned about the possible negative effects that watching stereo 3D content might possibly bring, and there are even speculations that it could even lead to permanent damage to the viewer’s eyes if watching too much 3D content on a daily basis. It is true that there haven’t been too much tests regarding this being done, but there are also no cases that confirm that watching stereo 3D content can lead to some health risks. Actually the only real concern is for small kids while their eyes and brain are still being developed, so maybe just in case you should be careful there is you have children. Other than that you can experience some short-term lets call them side effects from watching stereo 3D content like a movie, TV show, playing a game etc. and at least half of the time the reason for you getting uncomfortable, your eyes feeling tired, getting disoriented etc. is due to being exposed to badly shot or converted 3D content.

But beyond those short-term effects is there risk of permanent eye damage from exposing eyeballs to the faux third dimension for prolonged periods of time? That is what Gamasutra has asked a specialist – Dr. Mark Borchert, a respected L.A.-based ophthalmologist with the American Academy of Ophthalmology and here is what he answered:

It’s not likely to cause any permanent harm to vision. There are people who get uncomfortable with it, and get eye strain or headaches, or on much rarer occasions, a sense of imbalance or nausea, but there’s no evidence it can cause permanent harm to your vision or use of both eyes together or anything like that.

However while Borchert admitted that ophthalmologists “don’t have an answer” to the negative effects of 3D effect viewing on young children, the expert pegged the appropriate 3D viewing age even lower than Nintendo.

Binocularity and stereoscopic vision is something that is learned in the first few years of life, primarily in about the first three years of life. So it’s unlikely that children at that age, where stereoscopic vision is developing most critically, are going to be playing these games. But the effect of 3D on young children, we have no idea. For older children, it’s not going to hurt them. I can’t imagine how this is going to cause any kind of permanent harm to someone who is over four years of age.

Here I can personally confirm that being exposed to “fake” 3D content on computer screens, HMDs, paper prints and other sources for years I have no problems with my normal stereoscopic vision whatsoever, but then again I’m also well over three years old. And regarding the uncomfortable and more tiring first experience that most people have when they watch some 3D content for the first time, there is another scientific explanation, but simply said the main reason is that it is something new, and our eyes and brain need some time to adjust to it. So you should not get discouraged about watching stereo 3D movies or playing games in stereo 3D mode just because you first experience was a bit uncomfortable, try again a few times and if you still don’t get used to it, then you might have some trouble with your eyes or something else, so you should go and see a specialist just in case.

And now what is the actual and a bit more technical reason for the first maybe not so comfortable experience of some 3D content when you are exposed for more than a few minutes. The way that out eyes normally work is that they perceive the depth we are seeing by converging our eyes at an object we want to focus on based on the distance to it – for close objects they converge more and for more distant objects they may even remain parallel. And this movement of the eyes is achieved by the extraocular muscles of which each eye has six, and these muscles are responsible for it’s movement and depending on the distance to the object you are focusing on the eyes need to move in order to converge with the right angle. Then you also have the eyes focus differently depending on the distance to the object you converged your vision on and that is done by changing the curvature of the lens inside your eyes with the help of the ciliary muscles. These two things happen together in order for us to perceive the depth of real world objects in the real life when we are not watching stereo 3D content on out computer or TV screen…

However when watching 3D content on a screen there is something different and new to out eyes and brain and that is exactly what tires you at first, because you need some time to adjust to the new “sensation” and learn how to properly do it. You can even say that your eye muscles need to be trained too, although it is not only up to the muscles not being ready for the additional load they need to handle when watching stereo 3D content. As already mentioned while we are babies and small kids our binocularity and stereoscopic vision is being developed and we learn how to see and perceive the distance and depth of everything in the world around us. And since we use the method described above in the real world and try to apply the same when watching stereo 3D content on a flat screen, we try to do things the same way at first, but in case of “fake” 3D content displayed on screen there is something different. Normally when you are watching an object at a distance of lets say 10 meters away form you, your eyes are first converging for that distance of ten meters and then they focus for the same distance of 10 meters. However when watching a stereo 3D movie or playing a game in stereo 3D mode our eyes are still having to converge for a different distance depending on what content is being currently displayed on the monitor (lets say the 3D screen is 1 meter away from the viewer), so if you get an object that appears deeper inside the screen your eyes will let’s say converge for a distance of 3 meters or if something jumps out of the screen they will converge for lets say half a meter. So this way the first part is the same, our eyes still converge differently depending on the sense of volume (depth or pop-out) we have of the objects displayed on the 3D screen although the screen is actually sitting at a fixed position. However regarding the distance that out eyes need to focus at, depending on the object being displayed on a 3D screen, things are a bit different compared to the real world, as if you converge on an object that is 3 meters away from you in the real world your eyes will also focus for a 3 meter distance. But when you are watching the same thing on a 3D display your eyes will still converge for a 3 meter distance, but the focus you will get will not be for 3 meters like in the real world, but will instead remain at 1 meter – the distance to where your 3D monitor is. Now this is the exact reason that at first the stereo 3D content feels a bit weird, unreal and tiring for our eyes and brain, but after watching a second or third movie or trying to play a game for a few times in stereo 3D mode we adjust and we can easily do this different way of seeing things without feeling strain.

And now comes the role of bad 3D content like movies that were converted from 2D to 3D and that conversion hasn’t been properly made. Going to such a movie can have all the bad effects you’ve felt the first time when you watched some stereoscopic 3D content and in result can create a bad image for the movie (which is to be expected), but also can draw away people from stereo 3D in general usually because of them not knowing the difference between good and bad 3D and/or not knowing that they have actually watched a movie shot in 2D and then badly converted in 3D. The problem with bad conversions to 3D is that generally they contain contradicting depth cues or objects that our brain tells us that should be closer to us, but our eyes tell us just the opposite – that they should be very far form us. This again leads to some additional strain for both the brain and the eyes that are contradicting each other, but there can also be a lot of other factors that can lead to bad experience like jumping through fast scenes all the time with very far and very close objects with our eyes having to readjust to these changes too quick and too much and so on. And then again there should be no health risks associated with watching even badly converted 2D to 3D content, it just leaves a long term bad experience and may as well drive that person away from 3D for a while. However bringing small kids younger than 3 years to watch a badly converted 2D to 3D movie, or exposing them to an autoconverted 2D to 3D TV show or a movie at home on the new 3D HDTV is definitely not a good idea!

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3D Movie Making: Stereoscopic Digital Cinema from Script to Screen

May 12th, 2010 · 7 Comments · Other S3D Tech

I’ve been looking for a good book, written more recently and starting by covering how our stereoscopic vision works and then how its way of functioning can be taken advantage of in order to create the appropriate stereoscopic 3D content. A book that starts from the basics on how and why we see with depth and what it means to create a suitable digital content in 3D, that can be comfortably viewed in stereo 3D. It has turned out to be a quite hard task, but finally I was able to find such a book and it is called 3D Movie Making: Stereoscopic Digital Cinema from Script to Screen written by Bernard Mendiburu. The book is mainly targeted at people interested in 3D movie productions, but at the same time it covers all the basics of stereoscopic depth perception quite well and I found a lot of interesting things that I was not aware of. Of course it will be best if you are interested in 3D photography and 3D movies as this is the main focus of the book and especially how they are being produced and the specifics that the 3D format introduces. Even if you are interested only in stereo 3D gaming, you’ll still find a lot of information to help you understand how to achieve better results when tweaking the depth and convergence settings inside the game and why some games may give you problems even though they might seem to be rendered just fine in stereo 3D. The book also has an extensive list of references to useful websites and products – both free and commercial, that can help you in a lot of different 3D projects, especially if you consider to start shooting photos in 3D or even working on a stereo 3D amateur movie. For me the book was a great read and I’ve read it completely in one day, although it is over 200 pages, as it was indeed an interesting material to read and I could not stop myself until I’ve completely finished it. For me it was mostly stereo 3D gaming up until recently, but I’m starting to develop more and more interest in shooting photos and videos in 3D, so the whole book was full with useful information, and I can definitely recommend it to anyone really interested in stereo 3D…

3D Movie Making: Stereoscopic Digital Cinema from Script to Screen (Paper Book)

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